Furnaces for the recovery of metals, such as aluminium, are well known. Increasingly there is a demand for such furnaces, as legislation tends to encourage recovery and recycling of materials, particularly waste metals. There are also environmental benefits in recovering waste metals, rather than mining and smelting virgin ore. Aluminium is particularly well suited for mixing recovered (waste) aluminium with new aluminium material.
For the purposes of the present specification and the understanding of the invention, the furnace, its methods of operation and control will be described with reference to recovery of aluminium. However, it will be understood that variation to materials, operating conditions and parameters may be made so as to modify the furnace in order to enable recovery of other non-ferrous metals.
Furnaces for recovering waste aluminium have a heating system which melts the aluminium. A flux is introduced into the furnace to assist with the aluminium recovery. The flux generally consists of NaCl and KCl, other chemicals such as cryolite, may be added to the flux. The flux or salt cake assists in the process and is a well-known art. At elevated temperatures, typically from 200° C. -1000° C., the melted flux floats on the molten aluminium, as it is less dense. Pouring of recovered liquid aluminium is then possible by tipping or tilting the furnace in such a way that the flux remains in the furnace.